Increasing prevalence of allergic diseases has been noted in most developed and developing countries. Allergic diseases are defamed as functional disturbances caused by type I hypersensitivity, i.e., type I immune response mediated by IgE antibodies. The symptoms include pollinosis, bronchial asthma, allergic rhinitis, atopic dermatitis, and anaphylactic shock. Today, allergic diseases tend to be more severe in civilized societies and have cost a lot of money. Among the people who are suffering from various allergic symptoms, allergic rhinitis is the most common form of allergy. Also, the attack of allergen can sometimes be fatal. According to a statistic data of 1994 conducted by he Pediatrics Department of the Medical College of National Taiwan University, the prevalence rate of allergic rhinitis among students in Taipei city (Taiwan) is over 33%, about 3 times higher than that of asthma (10˜11%). The number of patient is also increasing every year. In particular, young child patients are on rapid rise. Thus, many researchers are devoting themselves in developing an improved solution to reduce economic and physical burden of the patient from such allergic diseases.
The initial stage of allergic reaction is development of IgB antibody that makes a strong combination with the mast cell or receptors on the surface of basophilic leukocyte. After the antigen or allergen being eaten by antigen-presenting cells such as macrophages, the peptide presented by MHC class II molecule on the surface of membrane is recognized by receptors on the surface of T-cell. Cell-activating substance (cytokines), such as IL-2, IFN-γ and TNF (tumor necrosis factor)-β (derived from Th1-cells), and IL-4, IL-5, IL-6, IL-9 and IL-10 (derived from Th2-cells), are produced in the activated T-cells. The produced cell-activating substance acts on T and B cells to participate in proliferation and differentiation. Then, B-cells are activated by the combination of CD40 ligand an T-cells and CD 40 on B-cells. Furthermore, as IL-4 derived from T-cells is added, B-cells are differentiated into IgB producing cells by a class switch. In the mast cells, two molecules of IgE are combined with polyvalent antigen to form a bridge on the receptors of membrane, leading to a series of biochemical processes causing degranulation. Various chemical media such as histamine are secreted from the mast cell by degranulation, and may increase the permeability of capillary, contract the smooth muscle, and enhance the mucus secretions, together with prostaglandins and leukotrienes produced newly by arachidonic acid metabolism within the membrane, which results in the followings: pruritis, flare, urticaria and angioedema on the skin; coughing, suffocating, chest tightness, respiratory difficulties and cyanosis in the respiratory tract; paling, hypotension and arrhythmia in, cardiovascular system; nausea, vomiting and diarrhea in GI tract; and paresthesia, vertigo, headache, convulsion and loss of consciousness in the nerve system.
The medicines used currently in alleviating various allergic symptoms have the problem that the effects thereof are temporary, and some side effects may occur by a long-term therapy. The antibiotics cannot affect the inhibition of IL-6 that is known for playing an important role in pathogenesis of chronic mucous exudates that are progressed in young children. It has been suggested that IL-6 could be controlled through antibiotic and steroids for a long period of time. However, administration of antibiotics and steroids for a long time may cause such side effects as suppressing immune function of the whole body.
The present inventors have made extensive clinical researches and experiments with the intention to find a novel treatment for various allergic diseases without any side effect. As a result, the inventors have found that a suitable nucleotide analog, ribavirin, possesses an excellent anti-inflammation effect without common side effects, and thus completed the present invention. In particular, the method and composition according to the present invention may increase immunity of a host to inhibit inflammation and control allergy.